Update README (#51)

* Update README

Updated create new project steps based on https://github.com/operator-framework/operator-sdk/blob/master/README.md,
```
INFO[0000] Creating new Go operator 'memcached-operator'. 
Error: dependency manager "modules" requires working directory to be in $GOPATH/src and GO111MODULE=on, or outside of $GOPATH/src and GO111MODULE="on", "auto", or unset. More info: https://github.com/operator-framework/operator-sdk/blob/master/doc/user-guide.md#go-modules
```

* Update README

Removing `--repo github.com/example-inc/memcached-operator`.

Author: akoserwal

README.md

@@ -23,6 +23,7 @@ Use the CLI to create a new `memcached-operator` project:
 ```sh
 $ mkdir -p $GOPATH/src/github.com/example-inc/
 $ cd $GOPATH/src/github.com/example-inc/
+$ export GO111MODULE=on
 $ operator-sdk new memcached-operator
 Create cmd/manager/main.go
 ...